feat(import): add the import page, multi-select add and the favorite platform

README.md

@@ -34,7 +34,17 @@ To Be Played is split into three repositories:
 - **Library**: status filters, "short games" filter (up to 10 h), search, sorting by playtime, recently seen, newest
   in library, rating or priority, paging. Each row shows the unlocked achievements.
 - **Add a game by name** for games outside Steam (PlayStation, Switch, Xbox, physical): search IGDB, pick a hit,
-  a platform and optional hours. Works without a Steam ID. Games already in ToBePlayed come first.
+  a platform and optional hours. Works without a Steam ID. Games already in ToBePlayed come first. Check several
+  hits to add them at once through the import review.
+- **Import** (`/import`): a list (one title per line) or a CSV (title, platform, hours or minutes, status). Core
+  matches the lines with IGDB and saves them in the background; the page shows the steps (queued with the imports
+  before yours, searching on IGDB, your review, adding to the library, time to beat and moods, done) with the
+  progress, and "Try again" for an import that stopped. The review shows the best match, other candidates and
+  "search again", with the platform and status per line. Only sure matches are checked. Earlier imports can be
+  undone.
+- **Platform everywhere**: each game shows its platform ("Steam" for Steam games). The favorite platform from the
+  settings is preselected when a game is on it; otherwise a game on one platform gets that one, and a game on
+  several waits for the user's pick.
 - **Game detail**: status, priority, 1–5 star rating, notes, achievements, time to beat (story / extras / 100 %),
   a link to the game's speedrun.com page when it has verified runs, a hint when Steam shows recent playtime for a
   game still in the backlog, and one to set the status to 100 % when